Browsing by Issue Date, starting with "2004-09-20"

Now showing 1 - 20 of 69477

Growth and characterization of tungsten carbide nanowires by thermal annealing of sputter-deposited WCx films
(2004-09-20)
Wang, SJ
;
Chen, CH
;
Chang, SC
;
Uang, KM
;
Juan, CP
In this letter, the growth of dense W2C nanowires by a simple thermal annealing of sputter-deposited WCx films in nitrogen ambient is reported. Straight nanowires with a density of 250-260 mum(-2) and length/diameter in the range of 0.2-0.3 mum/13-15 nm were obtained from the 700degreesC-annealed samples, which exhibit good electron field emission characteristics with a typical turn-on field of about 1.7 V/mum. The self-catalytic growth of W2C nanowires is attributed to the formation of alpha-W2C phase caused by carbon depletion in the WCx films during thermal annealing. (C) 2004 American Institute of Physics.
All-optical NRZ-to-PRZ format transformer with an injection-locked Fabry-Perot laser diode at unlasing condition
(2004-09-20)
Chang, YC
;
Lin, YH
;
Chen, JH
;
Lin, GR
;
光電工程學系
By using an optical nonreturn-to-zero (NRZ) format data-stream to injection-lock an synchronously modulated Fabry-Perot laser diode at below threshold condition (without DC driving current), an output data-stream with pseudo-return-to-zero (PRZ) format can be generated at bit rate of up to 2.488 Gbit/s. Such an NRZ-to-PRZ format transformation is due to the injection-locking induced gain-switching of the FPLD with the incoming NRZ data. The PRZ data-stream with a maximum on/off extinction ratio of 12.2 dB is obtained under the optical injecting power of -2 dBm and the RF driving power of 24.4 dBm. The best side-mode suppression ratio of 40 dB and the lowest timing jitter of 0.4 ps for the PRZ data-stream are observed. A power penalty of 1.2 dB is measured at a bit-error rate of 10(-9) after NRZ-to-PRZ transformation. In application, the demonstration of an all-optical OR logic gate using the FPLD-based NRZ-to-PRZ transformer is also reported. (C) 2004 Optical Society of America.
High performance CPW and microstrip ring resonators on silicon substrates
(2004-09-20)
Chen, CC
;
Hung, BF
;
Chin, A
;
McAlister, SP
;
電子工程學系及電子研究所
High performance CPW and novel microstrip ring resonators at similar to30 GHz and 40 GHz have been fabricated on Si substrates, using an optimized proton-implantation process. Very good insertion loss and resonator characteristics, close to those from ideal electromagnetic simulations, were measured. In contrast, the ring resonators on VLSI-standard Si, without implantation, have worse transmission and reflection loss, thus prohibiting applications in RF circuits. (C) 2004 Wiley Periodicals, Inc.
Vertical coupling effects and transition energies in multilayer InAs/GaAs quantum dots
(2004-09-20)
Li, YM
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
We investigate the transition energy of vertically stacked semiconductor quantum dots with a complete three-dimensional (3D) model in an external magnetic field. In this study, the model formulation includes: (1) the position-dependent effective mass Hamiltonian in non-parabolic approximation for electrons, (2) the position-dependent effective mass Hamiltonian in parabolic approximation for holes, (3) the finite hard-wall confinement potential, and (4) the Ben Daniel-Duke boundary conditions. To solve the nonlinear problem, a nonlinear iterative method is implemented in our 3D nanostructure simulator. For multilayer small InAs/GaAs quantum dots, we find that the electron-hole transition energy is dominated by the number of stacked layers. The inter-distance d plays a crucial role in the tunable states of the quantum dots. Under zero magnetic field for a 10-layer QDs structure with d = 1.0 nm, there is about 30% variation in the electron ground state energy. Dependence of the magnetic field on the electron-hole transition energy is weakened when the number of stacked layers is increased. Our investigation is constructive in studying the magneto-optical phenomena and quantum optical structures. (C) 2004 Elsevier B.V. All rights reserved.
Electron mobility in Ge and strained-Si channel ultrathin-body metal-oxide semi conductor field-effect transistors
(2004-09-20)
Low, T
;
Li, MF
;
Shen, C
;
Yeo, YC
;
Hou, YT
Electron mobility in strained silicon and various surface oriented germanium ultrathin-body (UTB) metal-oxide semiconductor field-effect transistors (MOSFETs) with sub-10-nm-body thickness are systematically studied. For biaxial tensile strained-Si UTB MOSFETs, strain effects offer mobility enhancement down to a body thickness of 3 nm, below which strong quantum confinement effect renders further valley splitting via application of strain redundant. For Ge channel UTB MOSFETs, electron mobility is found to be highly dependent on surface orientation. Ge<100> and Ge<110> surfaces have low quantization mass that leads to a lower mobility than that of Si in aggressively scaled UTB MOSFETs. (C) 2004 American Institute of Physics.
Tuning wavelength: Synthesis and characterization of spiro-DPVF-containing polyfluorenes and applications in organic light-emitting diodes
(2004-09-21)
Su, HJ
;
Wu, FI
;
Shu, CF
;
應用化學系
;
Department of Applied Chemistry
We have synthesized polyfluorene copolymers containing bis(2,2-diphenylvinyl)fluorene pendent groups attached orthogonally to the C-9 positions of fluorene units. These polymers possess high glass transition temperatures and good thermal stability. The results from PL studies indicate that most excitons formed in the polyfluorene backbone by direct photoexcitation are likely to migrate to lower-energy pendent groups, from which emission occurs. An organic light-emitting device using the copolymer PF4-DPVF as the emitting layer exhibits a voltage-independent and stable blue emission with color coordinates (0.15, 0.17) at 11 V, with a maximum brightness of 3137 cd/m(2) at 9 V (262 mA/cm(2)) and a maximum external quantum efficiency of 1.06%. In addition, we blended PF4-DPVF as the host material with 0.5 wt % of MEH-PPV to realize a white electroluminescence having CIE coordinates of (0.29,0.34) and a maximum brightness of 3258 cd/m(2) (119 mA/cm(2)). We demonstrate that both Forster energy transfer and direct charge trapping/recombination on the MEH-PPV guest are responsible for the observed EL.
MuSiC: a tool for multiple sequence alignment with constraints
(2004-09-22)
Tsai, YT
;
Huang, YP
;
Yu, CT
;
Lu, CL
;
生物科技學系
MuSiC is a web server to perform the constrained alignment of a set of sequences, such that the user-specified residues/nucleotides are aligned with each other. The input of the MuSiC system consists of a set of protein/DNA/RNA sequences and a set of user-specified constraints, each with a fragment of residue/nucleotide that (approximately) appears in all input sequences. The output of MuSiC is a constrained multiple sequence alignment in which the fragments of the input sequences whose residues/nucleotides exhibit a given degree of similarity to a constraint are aligned together. The current MuSiC system is implemented in Java language and can be accessed via a simple web interface.
The annealing behavior of copper deposit electroplated in sulfuric acid bath with various concentrations of thiourea
(2004-09-25)
Kao, YL
;
Tu, GC
;
Huang, CA
;
Chang, JH
;
材料科學與工程學系
The annealing behavior of electroplated copper deposits is reported in this study. The copper deposits were electroplated with a current density of 0.7 A/cm(2) at 53 degreesC in a sulfuric acid bath containing various concentrations of thiourea. The hardness values of the copper deposits were measured before and after annealing, and the differential scanning calorimetry (DSC) diagrams of the as-electroplated copper deposits were recorded. An improvement of the softening resistance of the copper deposits was observed when the bath contained thiourea greater than or equal to3 mg/L. By adding thiourea in the plating bath, smaller grain size of the copper deposits can be achieved. As thiourea content increased greater than or equal to3 mg/L, the twin boundary of the copper deposits was significantly increased, and many sulfur-rich particles were deposited along the grain boundaries and a few within the grains of the deposit. These sulfur-rich particles are capable of impeding migration of the grain boundaries and improving the softening resistance of the copper deposits during annealing. The aforementioned microstructures of the copper deposits were examined with transmission electron microscope (TEM) integrated with energy-dispersive X-ray spectrometer (EDX) for chemical composition analysis. (C) 2004 Elsevier B.V. All rights reserved.
Simple and efficient per-O-acetylation of carbohydrates by lithium perchlorate catalyst
(2004-09-27)
Lu, KC
;
Hsieh, SY
;
Patkar, LN
;
Chen, CT
;
Lin, CC
Lithium perchlorate is demonstrated to be a highly efficient and convenient catalyst for the per-O-acetylation of various saccharides with excellent yields. (C) 2004 Elsevier Ltd. All rights reserved.
On the Cl*(P-2(1/2)) reactivity and the effect of bend excitation in the Cl+CH4/CD4 reactions
(2004-09-30)
Zhou, JG
;
Lin, JJ
;
Zhang, BL
;
Liu, KP
;
應用化學系
The reaction of atomic chlorine with methane was studied in crossed-beam experiments at a collisional energy of E-c approximate to 4.7 kcal/mol. Using a time-sliced product imaging technique, several outstanding issues about this reaction were addressed in this work. It was found that the reactivity of the spin-orbit excited Cl*(P-2(1/2)) atom toward methane is negligibly small, in agreement with the assertion of recent studies. The excitation of methane bending/torsional modes exhibits only modest enhancement in reactivity, in contrast to the previous experiments. The product angular distributions are mainly backscattered for Cl + CD4, and sideways scattered for Cl + CH4. The shapes of the distributions from the ground state and the bend-excited methane are remarkably similar.
The super-connected property of recursive circulant graphs
(2004-09-30)
Tsai, CH
;
Tan, JJM
;
Hsu, LH
;
資訊工程學系
;
Department of Computer Science
In a graph G, a k-container C-k(u, v) is a set of k disjoint paths joining u and v. A k-container C-k(u, V) is K*-container if every vertex of G is passed by some path in C-k(u, v). A graph G is k*-connected if there exists a k*-container between any two vertices. An m-regular graph G is super-connected if G is k*-connected for any k with 1 less than or equal to k less than or equal to m. In this paper, we prove that the recursive circulant graphs G(2(m), 4), proposed by Park and Chwa [Theoret. Comput. Sci. 244 (2000) 35-62], are super-connected if and only if m not equal 2. (C) 2004 Elsevier B.V. All rights reserved.
Photodissociation of nitrosobenzene and decomposition of phenyl radical
(2004-09-30)
Tseng, CM
;
Choi, YM
;
Huang, CL
;
Ni, CK
;
Lee, YT
Photodissociation of nitrosobenzene in a molecular beam has been studied by multimass ion imaging techniques. Photodissociation at 248 nm shows that there is only one dissociation channel, i.e., C6H5NO --> C6H5 + NO, regardless of the fact that the other channel, C6H5NO --> C6H4 + HNO, is energetically accessible in agreement with theoretically predicted results. Photodissociation at 193 nm also shows the same dissociation channel. However, about 10% of the C6H5 radicals produced at this wavelength further decomposed into benzyne and H atom, and the dissociation rates of phenyl radical as a function of internal energies were measured. The averaged photofragment translational energies released from the dissociation of nitrosobenzene at 193 and 248 nm are 10.2 and 6.9 kcal/mol, respectively, and fragment distributions are almost isotropic at both wavelengths. In addition, the thermal rate constant for dissociation of C6H5NO has been computed and compared with experimental data; the agreement between theory and experiment is excellent, confirming the most recently reported unusually high A-factor (> 10(17) s(-1)).
Relic density of dark matter in brane world cosmology
(2004-10-01)
Okada, N
;
Seto, O
;
物理研究所
;
Institute of Physics
We investigate the thermal relic density of cold dark matter in the context of brane world cosmology. Since the expansion law in a high energy regime is modified from the one in the standard cosmology, if the dark matter decouples in such a high energy regime its relic number density is affected by this modified expansion law. We derive analytic formulas for the number density of dark matter. It is found that the resultant relic density is characterized by the "transition temperature" at which the modified expansion law in brane world cosmology is connecting with the standard one, and can be considerably enhanced compared to that in the standard cosmology, if the transition temperature is low enough.
Design of quasi-elliptic function filters with a dual-passband response
(2004-10-01)
Kuo, JT
;
Cheng, HS
;
電信工程研究所
;
Institute of Communications Engineering
Compact miniaturized hairpin resonators are used to design cross-coupled filters with a dual-passband response of elliptic function type. The hairpin resonators are treated as a stepped impedance resonator (SIR) in analysis. In a filter, two different hairpin resonators are used to establish proper couplings required for the two design frequencies. Two filters are fabricated and measured. The results show a good agreement with the simulation.
季．節．變．幻
(國立陽明大學, 2004-10-01)
陽明電子報編輯小組
秋光乍現，季節更迭，今年中秋適逢教師節，＜陽明人＞報導本校榮譽教授范秉真老師，范老師以校為家，一輩子作研究之精神，足為陽明人之典範。為落實導師制度，提昇師生交流情誼，本校實行已久的導師制度，頗獲好評。新學期的開始，召開全校性導師會議，除感謝老師們的辛勞，也提供導師們交流的管道。會議報導請詳閱＜焦點新聞＞。花亦芬老師應國科會人文處邀請，於九月八日至十六日間，赴歐洲義、德、法三國參訪歐洲藝術史研究中心與專業圖書館。返國後立即著手為本報撰寫此行之概述與感想，期能提供陽明師生一個更深刻、優質內涵，且多元豐富的人文藝術教育。全文請詳閱＜焦點新聞＞。開學了，校園中為了迎接新鮮人的加入，依例舉辦了一系列的活動，如衛保組即在九月廿日至十月五日間，辦理新生及全校教職員的急救訓練課程。＜焦點新聞＞在現場由本報特派員作全程報導，其中不乏令人發噱的場邊花絮，提供讀者親切的臨場感。＜社團動態＞看各系舉辦的迎新宿營，有熱鬧的活動，有開懷的節目，有逗趣的笑面，也有老師共襄盛舉。＜天涯行旅＞本期由生醫光電所黃彥臻報告他赴西班牙及摩洛哥的旅行，彥臻以窮學生自助旅行的方式，貼近當地真正的生活，與當地人聊天，聽他們聽的音樂，吃著和他們相同的麵包，快樂著他們的快樂。「旅行，就是為了尋找另一種生活的可能性」，看了真令人艷羨。＜脈脈含青＞左智慧到合歡山摘五顆星，並且和大家分享她在山坡上看到「晶瑩剔透」的高山杜鵑和松樹，令人感動的美景。＜藝事型態＞本期介紹保管組曲佩芬的編織作品，從串珠首飾、手機套，到圍巾、毛衣等，琳瑯滿目，美不勝收；每件作品都洋溢著濃郁的溫馨之情。陽明電
Low temperature MOSFET technology with Schottky barrier source/drain, high-K gate dielectric and metal gate electrode
(2004-10-01)
Zhu, SY
;
Yu, HY
;
Chen, JD
;
Whang, SJ
;
Chen, JH
Both P- and N-channel MOSFET's with Schottky barrier silicide source/drain (S/D), high-K gate dielectric and metal gate were successfully fabricated using a simplified low temperature process. The highest temperature after the high-K dielectric formation is 420degreesC. PMOSFETs with PtSi S/D show excellent electrical performance of an I-on/I-off similar to 10(7)-10(8) and a subthreshold slope of 66 mV/dec, similar to those formed by a normal process with an optimized sidewall spacer. NMOSFETs with DySi2-x S/D have similar to3 orders of magnitude larger I-off than that of PMOSFETs and show two slopes in the subthreshold region, resulting in the I-on/I-off similar to 10(5) at low drain voltage. It can be attributed to the relatively higher barrier height (Phi(n)) of DySi2-x/n-Si than that of PtSi/p-Si (Phi(p)) and the rougher DySi2-x film. Adding a thin intermediate Ge layer (similar to1nm) between Dy and Si can improve the film morphology significantly. As a result, the improved performance of N-MOSFET is observed. (C) 2004 Published by Elsevier Ltd.
A self-growing probabilistic decision-based neural network with automatic data clustering
(2004-10-01)
Tseng, CL
;
Chen, YH
;
Xu, YY
;
Pao, HT
;
Fu, HC
In this paper, we propose a new clustering algorithm for a mixture of Gaussian-based neural network and self-growing probabilistic decision-based neural networks (SPDNN). The proposed self-growing cluster learning (SGCL) algorithm is able to find the natural number of prototypes based on a self-growing validity measure, Bayesian information criterion (BIC). The learning process starts from a single prototype randomly initialized in the feature space and grows adaptively during the learning process until most appropriate number of prototypes are found. We have conducted numerical and real-world experiments to demonstrate the effectiveness of the SGCL algorithm. In the results of using SGCL to train the SPDNN for data clustering and speaker identification problems, we have observed a noticeable improvement among various model-based or vector quantization-based classification schemes. (C) 2004 Elsevier B.V. All rights reserved.
The edge-coloring of graphs with small genus
(2004-10-01)
Fan, HL
;
Fu, HL
;
應用數學系
;
Department of Applied Mathematics
In this note, we prove that a graph is of class one if G can be embedded in a surface with positive characteristic and satisfies one of the following conditions: (i) Delta(G) greater than or equal to 3 and g(G) (the girth of G) greater than or equal to 8 (ii) Delta(G) greater than or equal to 4 and g(G) greater than or equal to 5; and (iii) Delta(G) greater than or equal to 5 and g(G) greater than or equal to 4.
陽明電子報「天涯行旅」徵文及照片
(國立陽明大學, 2004-10-01)
陽明電子報編輯小組
就要Fun暑假了，驛動的心哪，也開始活蹦亂跳起來了吧？陽明電子報規劃新的專欄「天涯行旅」，請所有的陽明師生一起來投稿：無論國內、外的任何景點；文章長短、內容及形式不拘；若無文字僅附照片亦可，但須附圖片說明
Tumor necrosis factor-alpha-308 promoter and p53 codon 72 gene polymorphisms in women with leiomyomas
(2004-10-01)
Hsieh, YY
;
Chang, CC
;
Tsai, FJ
;
Lin, CC
;
Yeh, LS
Objective: Tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, plays an important role in the process of autoimmune diseases. p53 is related to the regulation of cell growth and prevention of carcinogenesis. We propose to investigate whether gene polymorphisms for TNF-alpha-308 promoter and p53 could be used as markers of susceptibility in leiomyomas. Design: Prospective basic study. Setting: Departments of gynecology and genetics in a medical center. Patient(s): Group 1: leiomyoma (n = 159); group 2: non-leiomyoma (n = 13 1). Intervention(s): Genomic DNA was obtained from peripheral leukocyte. The TNF-alpha and p53 gene polymorphisms were amplified by polymerase chain reaction (PCR), enzyme restriction, and electrophoresis. Main Outcome Measure(s): Two gene polymorphisms were identified: [1] the A (cuttable)/G (uncuttable) polymorphisms of the TNF-alpha gene on chromosome 6p2l.3; [2] A (cuttable)/P (uncuttable) polymorphisms of the p53 gene on chromosome 17p. Genotype and allelic frequencies in both groups were compared. Result(s): Genotype distribution and allele frequency of TNF-a gene polymorphism in both groups were significantly different. Proportions of A homozygote/heterozygote/G homozygote for TNF-alpha in both groups were: (group 1) 61%/34.6%/4.4% and (group 2) 81.7%/14.5%/3.8%. Proportions of allele A/G for TNF-alpha in both groups were: (group 1) 78.3%/21.7% and (group 2) 88.9%/11.1%. Distributions of p53 polymorphisms in both groups were not different. The proportions of A homozygotes/heterozygotes/P homozygotes for p53 were (group 1) 32.7%/42.1%/25.2% and (group 2) 28.2%/48.9%/22.9%. Conclusion(s): G homozygote and G allele for TNF-alpha promoter are related to a higher risk of leiomyomas. The p53 codon 72 gene polymorphism is not associated with the susceptibility of leiomyomas. (C) 2004 by American Society for Reproductive Medicine.